Circle hitTestPoint

eezing

New to Gideros here and needed a simple hitTestPoint for circle buttons. Searched the forum and the solutions posted although very good, appear to be a little too robust.

So here's the solution I came up with. Please post if something looks off or if some efficiency can be attained.

1. Duplicated the generic button class found in the Gideros 'button' example. Renamed class to 'ButtonCircle'.

2. Search and replace:

self:hitTestPoint(event.x, event.y) -- For this: self:ButtonCircleHitTest(event.x, event.y)

3. Add function this function to class:

-- Assumes: -- ButtonCircle is child to a parent button -- Parent button anchorPoint = (.5, .5)   function ButtonCircle:circleHitTest(eventX, eventY)   -- Get these if we don't have them yet if not self.myParent or not self.myRadius then self.myParent = self:getParent() self.myRadius = self.myParent:getHeight() * .5 end   local x, y = self.myParent:getPosition() -- Grab position from parent   -- Is touch distance from center within radius of circle? if self.myRadius > math.sqrt((eventX - x)^2 + (eventY - y)^2) then return true end end

talis

Thanks. Nice soluton.

ar2rsawseen

Great solution, thanks for sharing

john26

"too robust" you can't get too robust! :-)

A slight modification: compare the radius squared to distance squared. That way you can avoid taking the square root which is expensive:

self.myRadius^2 > (eventX - x)^2 + (eventY - y)^2

eezing

@john26

Ah yes, this good. Thanks for sharing.

tkhnoman

Great.

Also, if your object is in moving parent, you can use :
local x, y = self:localToGlobal(0,0)

jdbc

Use TNTCollision function to calculate collision between a point and a circle for better performance than math.sqrt or ^2 on lua.

Just check if the point (event.x, event.y) collides with the circle.

eezing

@tkhnoman

Yep, just ran into a problem with moving parent. Thanks for the tip.

@jdbc

I'm going to give this a shot... the video of the native demo looks pretty good.